Highly efficient synthesis of 3-amino-/alkylthio-cyclobut-2-en-1-ones based on the cyclization of acyl ketene dithioacetals

A new strategy for the highly efficient one-pot synthesis of 3-amino-/alkylthio-cyclobut-2-en-1-ones based on the cyclization of acyl ketene dithioacetals is disclosed. In addition, the rearrangement of 3-amino-cyclobut-2-en-1-ones to 4-quinolone derivatives is described.